In the manufacture of semiconductor devices, it is common to place small solder balls upon the substrate of the semiconductor device in a ball grid array and then reflow the solder balls in an oven to provide a series of electrical connections on the substrate. Currently, there are several different approaches for placing solder balls to form ball grid arrays onto semiconductors and other electrical devices.
In one approach, an array of solder balls is picked up with a vacuum head. Each solder ball is held by a separate vacuum nozzle in the vacuum head. The vacuum head then places the solder balls on the semiconductor substrate and releases the solder balls thereon.
In another approach, a mask is placed over the semiconductor substrate. The mask has an array of openings formed therethrough corresponding to the desired pattern of electrical connections on the substrate. A quantity of solder balls is then spread across the mask with an air knife or a squeegee. Some of the solder balls fall into and are captured by the openings in the mask thereby positioning the solder balls in the desired pattern on the substrate.
In still another approach, a transfer substrate is formed with an array of indentations corresponding to the desired pattern of electrical connections on the substrate. The array of indentations is then filled with solder balls. The semiconductor substrate is brought face down into contact with the array of solder balls lying on the transfer substrate. The solder balls are then reflowed and metallurgically bonded to the semiconductor substrate.